NREL Developed Silicon Carbide Inverter Part of Production Intent Program at John Deere

NREL-Developed Silicon Carbide Inverter Part of Production-Intent Program at John Deere

Nearly every modern convenience-from the electronic gadgets in our homes to the food that is farmed and transported to our tables-relies on one unsung hero: the semiconductor. Smaller than a fingernail, these powerful devices manipulate and control the flow of energy within electronic devices. In turn, they connect and power our world.

Now, in pursuit of a clean energy future, National Renewable Energy Laboratory (NREL) researchers are pushing the boundaries of these devices by creating the conditions to make them faster, lighter, more powerful, and more cost-effective than ever before. One of their efforts hinges on devices made from silicon carbide (SiC) semiconductors.

In collaboration with John Deere, one of the largest global agriculture equipment manufacturers in the world, and under the umbrella of the U.S. Department of Energy's PowerAmerica program, NREL researchers helped craft a 200-kilowatt, 1,050-volt SiC traction inverter with never-before-seen performance, capable of roughly 400% greater power density than previous silicon-only designs.

Now, the SiC technology is being adopted into a production-intent program across John Deere's vehicle platforms.

With a higher voltage capacity, a lower cost, a smaller footprint, and greater efficiency than virtually any heavy-duty vehicle inverter on the market, the inverter can enable John Deere's vehicles to operate at the same level as traditional designs but using less fuel. That can reduce operating costs and harmful emissions for sectors such as agriculture and construction.

"It took us five years to create the John Deere silicon carbide inverter. Then, once we had built it, it surpassed our expectations," said Brij Singh, electrification research and development (R&D) manager and the John Deere technical fellow who spearheaded the project. "By adopting a system approach, silicon carbide technology may lead to a performance-superior and cost-neutral solution from a total cost of ownership (TCO) standpoint. It exceeded our performance expectations. It even had a sustainability aspect-with a smaller housing, it cut down the carbon footprint of manufacturing."

Singh continued, "We saw that if we were innovative, if we invested in good engineering, and if we worked with NREL researchers who are eager to apply their ingenious solutions, we could indeed lower costs while seeing better performance."

A Better Building Block

The revolutionary performance of the new John Deere traction inverter can be traced to its building blocks: SiC-based semiconductors.

SiC semiconductors are superior in nearly every way to their predecessors, silicon power semiconductors. Unlike silicon, SiC can function at high temperatures and voltages-a critical ability, as traction inverters are typically housed near heat-generating components within a vehicle's motor.

Moreover, SiC has outstanding switching performance, meaning it can convert electricity from one form to another with lower losses than other materials. Because traction inverters are responsible for inverting, or switching, electricity into the multiple forms needed by a vehicle, SiC's superior switching enables a more energy-efficient system.

Taken together, SiC's characteristics allow it to form a better building block for the semiconductors that make up the John Deere traction inverter, in turn the heart of the vehicle's propulsion system.

NREL researchers played a key role in multiple aspects of the project-notably, its packaging and thermal management. Extremely powerful SiC-based inverters housed in a small package can experience higher heat flux, or thermal loading, which, if not dispersed, can prematurely degrade the system. NREL researchers applied their world-class expertise in power electronics thermal management and packaging to the problem.

Researchers from NREL's advanced power electronics and electric machines group developed a custom thermal management design that allows the John Deere inverter to share a coolant circuit with the vehicle's diesel engine. The innovative packaging and thermal management design allowed researchers to reduce the SiC inverter's size and weight while increasing its power density by 378% compared to John Deere's PD400 silicon inverter-all while simplifying the vehicle architecture. This led to not just increased energy efficiency and a reduction in fuel use per hour but also a lower manufacturing cost.

NREL's power electronics researchers also conducted extensive thermomechanical modeling to ensure the inverter could withstand the full range of John Deere's heavy-duty vehicle engine coolant temperatures, which can soar to 115°C. These evaluations indicated that the inverter can perform reliably, without risk of premature component failure.

With John Deere secure in the knowledge that the traction inverter could operate at high temperatures, under high pressure, and with full use of SiC's high-power conversion efficiencies at a lower cost, Singh verified the technology in John Deere's heavy-duty 644 K hybrid loader, used primarily in construction. Now, the traction inverter is set to be adopted into a production-intent program at John Deere.

"This was a very exciting collaboration that called on our decades of effort to develop the laboratory's power electronics modeling, thermomechanical reliability, and thermal management capabilities," said Sreekant Narumanchi, who leads NREL's power electronics and electric machines group. "To see John Deere pursuing the inverter in a production-intent program is the best testament to our efforts."

According to Singh, the NREL collaboration has helped accelerate John Deere's efforts toward cleaner, higher-performance machines.

It only remains to be seen which revolutionary technology NREL's power electronics researchers design, demonstrate, and characterize next-all in pursuit of a cleaner, more connected world.

Learn more about NREL's sustainable transportation and mobility research and its specific focus on power electronics and electric machines. And sign up for NREL's quarterly transportation and mobility research newsletter, Sustainable Mobility Matters, to stay current on the latest news.

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